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| United States Patent |
5,217,814
|
|
Kawakami
, et al.
|
June 8, 1993
|
Sintered sliding material
Abstract
The wear resistance and seizure resistance of the sliding material
consisting of a metal backing, a Cu-based sintered layer, and resin and
solid lubricant filled in the pores of the sintered layer are improved by
determining the following features (a) multi-layer Cu particles; from 30
to 200 .mu.m of the diameter of the Cu particles; porosity of from 5 to
70% of the sintered layer; resin, MoS.sub.2 and graphite filled in the
pores.
| Inventors:
|
Kawakami; Shinya (Aichi, JP);
Miziguchi; Shinichi (Aichi, JP);
Fukuoka; Tatsuhiko (Aichi, JP);
Kabeya; Yasunori (Aichi, JP);
Shimasaki; Keiichi (Aichi, JP)
|
| Assignee:
|
Taiho Kogyo Co., Ltd. (Aichi, JP)
|
| Appl. No.:
|
831249 |
| Filed:
|
February 7, 1992 |
Foreign Application Priority Data
| Feb 09, 1991[JP] | 3-037820 |
| Oct 09, 1991[JP] | 3-290578 |
| Mar 02, 1992[JP] | 4-047544 |
| Current U.S. Class: |
428/545; 75/231; 75/243; 75/244; 75/247; 428/546 |
| Intern'l Class: |
B22F 003/24; B22F 007/00 |
| Field of Search: |
75/231,243,244,246
428/547,551,559,561,565,545
|
References Cited
U.S. Patent Documents
| 3705450 | Dec., 1972 | Morisaki | 428/545.
|
| 3883314 | May., 1975 | Schnyder et al. | 29/182.
|
| 3914178 | Oct., 1975 | Fineran et al. | 252/12.
|
| 4208472 | Jun., 1980 | Cho et al. | 428/550.
|
| 4505987 | Mar., 1985 | Yamada et al. | 428/552.
|
| 4655944 | Apr., 1987 | Mori | 252/12.
|
| 4666787 | May., 1987 | Bickle et al. | 428/550.
|
| 4680161 | Jul., 1987 | Muto | 419/3.
|
| 4716766 | Jan., 1988 | Baureis | 73/827.
|
| 4740340 | Apr., 1988 | Pratt et al. | 264/171.
|
| 5024882 | Jun., 1991 | Matucha et al. | 428/323.
|
| 5041339 | Aug., 1991 | Mori et al. | 228/552.
|
| 5089354 | Feb., 1992 | Nakashima et al. | 428/552.
|
| Foreign Patent Documents |
| 44577 | Jan., 1982 | EP | 428/550.
|
| 53-36856 | May., 1978 | JP.
| |
| 55-106230 | Aug., 1980 | JP.
| |
| 61-192738 | Aug., 1986 | JP.
| |
| 63-37445 | Jul., 1988 | JP.
| |
| 2139236 | Nov., 1984 | GB.
| |
Primary Examiner: Walsh; Donald P.
Assistant Examiner: Mai; Nguoclan T.
Attorney, Agent or Firm: Armstrong, Westerman, Hattori, McLeland & Naughton
Claims
We claim:
1. A sliding material comprising a metal backing; and a layer comprising
multi-layers of sintered Cu or Cu-alloy particles 30 to 200 .mu.m in
diameter deposited on the metal backing; said layer having from 5 to 70%
by volume of pores filled with additives comprising a resin and solid
lubricant, said lubricant comprising from 30 to 80% by weight of
molybdenum disulfide and graphite based on weight of the additives;
wherein the surface of said layer is machined and contains 30-95% of said
Cu or Cu-alloy and the balance is said additives.
2. A sliding material comprising a metal backing and a layer comprising
layers of sintered Cu or Cu-alloy particles 30 to 200 .mu.m in diameter
deposited on the metal backing; said layer having from 5 to 70% by volume
of pores filled with additives comprising a resin and a solid lubricant,
said lubricant consisting of from 30 to 80% by weight of molybdenum
disulfide and graphite and from 3 to 20% by weight of a at least one
member selected from the group consisting of tungsten disulfide, BN,
fluorine plastics, and Pb based on weight of the additives; wherein the
surface of said layer is machined and contains 30-95% of said Cu or
Cu-alloy based on the surface area of the machined surface and the balance
is said additives.
3. A sliding material according to claim 1 or 2, wherein said machined
surface comprises 85% or less of said Cu or Cu-alloy.
4. A sliding material according to claim 3, wherein said machined surface
comprises from 30 to 80% of said Cu or Cu-alloy.
5. A sliding material according to claim 1 or 2, wherein said additives
comprise from 35 to 55% by weight of molybdenum disulfide and graphite.
6. A sliding material according to claim 5, wherein said molybdenum
disulfide is filled in the pores of the sintered Cu or Cu-alloy in an
amount cf from 10 to 50% by weight based on the weight of the additives
and the Cu or Cu alloy.
7. A sliding material according to claim 6, wherein said molybdenum
disulfide is filled in the pores of the sintered Cu or Cu-alloy in an
amount of from 15 to 35% by weight based on the weight of the additives
and the Cu or Cu alloy.
8. A sliding material according to claim 5, wherein said graphite is filled
in the pores of the sintered Cu or Cu-alloy in an amount of from 2 to 40%
by weight based on the weight of the additives and the Cu or Cu alloy.
9. A sliding material according to claim 8, wherein said graphite is filled
in the pores of the sintered Cu or Cu-alloy in an amount of from 15 to 30%
by weight based on the weight of the additives and the Cu or Cu alloy.
10. A sliding material according to claim 1 or 2, wherein said additives
comprise from 20 to 70% by weight of the resin.
11. A sliding material according to claim 10, wherein said resin is
selected from the group consisting of aromatic polyimide resin and a
modified resin of aromatic polyimide resin.
12. A sliding material according to claim 10, wherein said resin is phenol
resin.
13. A sliding material according to claim 1 or 2, wherein said porosity is
from 10 to 60%.
14. A sliding material according to claim 13, wherein said porosity is from
30 to 50%.
15. A sliding material according to claim 1 or 2, wherein said Cu or
Cu-alloy particles comprises irregularaly shaped particles having an
average-long diameter of from 30 to 200 .mu.m.
16. A sliding material according to claim 15, wherein 50% or more of said
alloy particles is said irregularly shaped particles, whose ratio of
short-diameter/long-diamter is from 0.2 to 0.7.
17. A sliding material according to claim 1 or 2, produced by sintering
said Cu or Cu-alloy onto the metal backing, impregnating the pores of
sintered Cu or Cu-alloy with said additives, and then machining the
surface of the sintered layer to a depth of at least 100 .mu.m.
Description
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to a sliding material having improved sliding
properties under a mixed lubricating condition and a boundary lubricating
condition. More particularly, the present invention relates to a sintered
sliding material, which consists of metal backing, a Cu or Cu-alloy layer
sintered on the metal backing, and resin and solid lubricant which are
filled in the pores formed in the sintered layer around the particles of
the Cu or Cu-alloy.
2. Description of Related Arts
It is known from Japanese Unexamined Patent Publication No. 55-106,230 that
30% by weight or less of polyimide and such lubricating additives as
molybdenum disulfide and graphite can be filled in the pores of a sponge
metal, e.g., Cu, having porosity of from 88 to 98%. The sponge metal
having a very large porosity is the substrate material which supports the
filled materials. As is described in said publication, the blanking of the
sponge metal is usually necessary for shaping it into the form of a
bearing. The recovery of the workpieces by the blanking is, however,
disadvantageously low. In addition, the formability of the sponge metal is
poorer than that of the sliding material which comprises the metal
backing.
Japanese Examined Patent Publication No. 63-37445 discloses a sintered
sliding material of the type described above. That is, a Cu or Cu-alloy
layer is sintered on the metal backing, and resin and solid lubricant are
filled in the pores of the sintered layer. The surface of the sliding
material is machined to expose the sintered metal and the filled material.
The surfaces of the sintered metal and the filled material therefore form
an essentially identical plane.
According to the method for producing the sliding material described in
Japanese Examined Patent Publication No. 63-37445, an almost spheroidal
lead-bronze powder, having a diameter of 0.18 mm, is sintered on the metal
backing and then machined to provide a thickness of 0.11 mm. The thus
machined sintered metal is exposed on the surface of the sliding metal at
40-60% of such surface. It is also disclosed in Japanese Examined Patent
Publication No. 63-37445 that such solid lubricants as molybdenum
disulfide and graphite are desirably limited to an amount of 30% by weight
or less. In this case, the amount of the polyimide and polyamide-imide,
having a high bonding strength, increases relative to the solid lubricant,
and, thus, the effects of the solid lubricant are not outstanding.
Other drawbacks of the known sliding material are described with reference
to FIG. 4.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a graph illustrating the relationship between the exposed area of
the sintered metal layer and the seizure time.
FIG. 2 is a graph illustrating the relationship between the exposed area of
the sintered metal layer and the amount of wear.
FIG. 3 is a graph illustrating the relationship between the exposed area of
the sintered metal layer and the coefficient of friction.
FIG. 4 is a graph illustrating the relationship between the exposed area of
the sintered metal layer and the machining depth.
FIG. 5 is a photograph showing the sintered layer consisting of spheroidal
Cu-based powder.
FIG. 6 is a photograph showing the sintered layer consisting of irregularly
shaped Cu-based powder.
EXPOSED AREA OF SINTERED LAYER
When the sintered layer is a mono-layer of metal particles and is subjected
to machining, the exposed area of the sintered layer greatly varies
depending upon the machining depth. The sliding properties of such sliding
material are very unstable, because the exposed area of the sintered metal
determines the sliding properties in such a manner that the metal contact
between the sliding material and the opposed material increases with the
increase in the exposed area, and, thus, wear-resistance is enhanced and
seizure-resistance is lowered with the increase in the exposed area.
When the metal particles are piled on one another, a multi-layer sintered
material is provided. In this case, if the metal particles are piled at
the geometrically highest density, the exposed area of the sintered metal
layer does not vary irrespective of the machining depth. In actuality,
however, the exposed area of the sintered metal layer varies as is
illustrated in FIG. 4.
In FIG. 4, the sliding layer was prepared as follows.
Spheroidal Cu powder having an average particle diameter of 110 .mu.m was
piled to form an almost three layered material (that is, two to three
layers in all areas) and then sintered. The so-prepared sintered layer had
a thickness of approximately 300 .mu.m and approximately 35% by volume of
porosity. The entire sintered layer was impregnated with resin in such a
manner that the resin protruded above the surface of the sintered layer by
a height of approximately 20 .mu.m. The so-prepared sliding material was
machined at a depth given in the abscissa of FIG. 4. The exposed area of
the sintered layer dependent upon the machining depth is given in the
ordinate of FIG. 4. As is clear from FIG. 4, it is necessary to machine,
by a depth of 100 .mu.m or more, the sintered particles piled on one
another to form a multi-layered, material, in order to stabilize the
exposed area of the sintered metal layer.
When the exposed area of the sintered metal mono-layer is very low, e.g.,
approximately 20%, it would greatly vary when the machining depth shifts
from the predetermined one. The siding properties vary therefore greatly
between the production lots. In addition, when the resin wears out
slightly during the sliding, the exposed area of the sintered layer
abruptly increases, thereby greatly changing the sliding properties.
The change in the exposed area of the sintered layer may occur during the
initial sliding period while the roughness of the sliding surface is not
yet compaticle to that of the opposed material. This case is very
disadvantageous, because either the sliding material or the opposed
material may abruptly wear out due to the metal contacts therebetween,
thereby causing seizure.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a sliding
material which can overcome the drawbacks of the heretofore known sliding
materials, and which has the following features:
(1) the sliding properties are stable irrespective of slight variations in
the machining depth of the sliding surface;
(2) seizure resistance does not abruptly deteriorate when the sliding
surface slightly wears out; and,
(3) wear-resistance and seizure-resistance are excellent under severe
sliding conditions.
In accordance with the objects of the present invention, there is provided
a sliding material, which comprises:
a metal backing;
multi-layer Cu or Cu-alloy particles sintered on said metal backing,
consisting of metal particles from 30 to 200 .mu.m in diameter and piled
on one another in at least two layers; said metal particles forming a
sintered layer having from 5 to 70% by volume of pores;
a resin and solid lubricant (hereinafter referred to as the additives)
filled in said pores, said lubricant comprising from 30 to 80% by weight
of molybdenum disulfide and graphite based on the weight of the additives;
and,
a machined surface at the top of the siliding material, consisting of said
Cu or Cu-alloy in an amount of 95% or less based on the area of said
machined surface, the balance being said additives.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention is hereinafter described in detail.
The metal backing may be of any known kind.
The Cu or Cu-alloy of the sintered layer may be pure Cu or Cu alloys, such
as bronze, lead bronze, and phosphor bronze. A powder of FeP, Al.sub.2
O.sub.3 or the like may be dispersed in the Cu or Cu-alloy described above
to provide composite material, which may also be used as the Cu-alloy in
the present invention. The Cu or Cu alloy powder is sintered on the metal
backing to form a sintered layer.
The Cu-based Powder is spheroidal, virtually spheroidal without sharp
edges, or irregularly shaped, e.g., flaky, dendritic, chain-shaped or
scalene polygonal.
When the irregular powder is used, 50% or more, preferably 70% or more of
the total powder must be the irregular powder, whose ratio of
short-diameter/long-diameter is from 0.2 to 0.7 whose ratio of
short-diameter/long-diameter is from 0.2 to 0.7. When 50% or more of the
total powder is the irregular powder, whose ratio of short-diameter/long
diameter is more than 0.7, the effects of the irregular powder are not
outstanding. On the other hand, when 50% or more of the total powder is
the irregular powder, whose ratio of short-diameter/long diameter is 0.2
or less, pores of the total powder are so decreased that desirable filling
density is not obtained. Since the pores are liable to be
disadvantageously densely filled with this irregular powder, the amount of
this irregular powder should desirably be limited to 30% or less,
particulary 10% or less of the total powder.
The average size of the powder particles of the sintered layer is from 30
to 200 .mu.m, preferably from 50 to 200 .mu.m, and more preferably from 60
to 150 .mu.m. The average long-diameter of the irregular powder must be
from 30 to 200 .mu.m. When this size is less than 30 .mu.m, and, further,
when the filling density of the powder is high, for example 5g/cc, it is
difficult to impregnate the pores of sintered layer with the resin and
solid lubricant. On the other hand, when this size is more than 200 .mu.m,
and, further, when the filling density of the powder is low, for example
2.5g/cc, the bonding strength of the Cu (alloy) particles of the sintered
layer becomes disadvantageously low.
The porosity in volume % of the sintered layer is from 5 to 70%, preferably
from 10 to 60%, and more preferably from 30 to 50%. When the porosity is
less than 5%, the impregnated amount of the resin and solid lubricant is
so reduced that such sliding properties as low-friction and lubrication
property are impaired and thus seizure is liable to occur. On the other
hand, when the porosity is more than 70%, the proportion of the sintered
metal is so reduced that the strength is disadvantageously reduced.
The proportion of sintered metal on the sliding surface, i.e., the exposed
area of the sintered layer, is 95% or less, s preferably 85% or less, and
more preferably from 30 to 80%. When the exposed area of the sintered
layer is more than 95%, the effects of the solid lubricant are not
attained.
The preferred exposed area, in accordance with the application of the
sliding material is: high area %, i.e., 60-80% for ordinary conditions;
and, low area %, i.e., 40-60% for severe sliding conditions where seizure
is likely to occur. This exposed area of the sintered layer exerts great
influence on the surface properties of the sliding material at a portion
thereof facing the opposite material. This was also an influencing factor
in the known sliding material but greatly varied, depending upon the
production conditions. Therefore, the intended sliding properties cannot
be attained by controlling the exposed area of the sintered layer in the
known material. Contrary to this in the present invention, since the
multi-layer sintered metal particles are formed on the metal backing,
great variation in the exposed area of the sintered layer can be
prevented, and the sliding properties can be controlled by controlling the
exposed area.
The porosity is smaller as the particle diameter of the powder gets
smaller, because the sintering is liable to be promoted. However, when the
large-diameter particles and small-diameter particles are mixed, such a
mixed powder causes a reduction of porosity, although the average particle
diameter of the mixed powder is the same as that of a powder having
uniform particle diameter. The porosity described as a feature of the
invention indicates an average porosity. The local porosity of the
sintered layer varies and is large at the surface of the sliding layer as
is shown in FIG. 4.
A feature of the sintered layer according to the present invention is the
multi-layer of metal particles piled on one another. When the metal
particles are dispersed on the metal backing but are not piled on one
another, a mono-layer of metal particles is formed. When the mono-layer of
metal particles is sintered and then machined on the surface of the
sintered layer, it is difficult to attain by machining a stably constant
exposed area of the sintered layer. In addition, parts of the metal
particles may be separated from the metal backing after the sintering,
and, therefore, the exposed area is unstable in the case of the mono-layer
of metal particles. Contrary to this, in the case of the multi-layer metal
particles, the exposed area of the sintered layer becomes stable provided
that the surface of sintered layer is machined to a certain depth as is
shown in FIG. 4.
The sintered layer consisting of spheroidal metal particles as shown in
FIG. 5 has a higher exposed area of the sintered layer as compared with
the sintered layer consisting of irregularly shaped metal particles as
shown in FIG. 6, by 15-20% over almost the entire range of the machining
depth.
The dimension of the irregular powder shown in FIG. 6 is as follows.
______________________________________
Average long-diameter - 90 .mu.m
Proportion (%)
Ratio of long-diameter/Short/diameter
in total powder
______________________________________
less than 0.2 4
0.2-0.7 76
more than 0.7 20
______________________________________
The filling density of the spheroidal metal particles is from 4.4 to 4.8
g/cc (volume of the sintered layer), while the filling density of the
irregularly shaped metal particles is from 3.2 to 3.7 g/cc. The low
filling density of the latter corresponds to the smaller exposed area of
the latter, while the high filling density of the former corresponds to
the large exposed area of the former. The exposed area of the irregularly
shaped metal particles is from 30 to 60% at the machining depth of from 50
to 150 .mu.m. This exposed area corresponds to the range of FIG. 1, where
the seizure resistance is high.
The preferred average filling density of the irregularly shaped powder is
from 2.5 to 4.0 g/cc, particularly from 2.8 to 3.7 g/cc. The average
filling density in FIG. 6 is 3.5 g/cc.
The additives contain from 30 to 80% by weight, preferably from 35 to 55%
by weight of molybdenum disulfide and graphite as the solid lubricant. The
molybdenum disulfide enhances the seizure-resistance, and the graphite
enhances the wear-resistance. When the solid lubricant is less than 30% by
weight, the seizure and wear are likely to occur under mixed lubricating
conditions and boundary lubricating conditions. On the other hand, when
the solid lubrincant is more than 80% by weight, the molybdenum disulfide
and the like are liable to be removed from the sliding material during
use. The balance of the solid lubricant is the resin.
The molybdenum disulfide contained in the sliding layer is preferably in an
amount of from 10 to 50% by weight, more preferably form 15 to 35% by
weight. The molybdenum disulfide
preferably has an average diameter of from 0.5 to 25 .mu.m. The graphite
contained in the sliding layer is preferably in an amount of from 2 to 40%
by weight, more preferably from 15 to 30% by weight. The graphite
preferably has an average diameter of from 8 to 35 .mu.m. The graphite may
be a natural or synthetized one. Isotropic synthetized graphite is
preferable in the light of wear resistance.
For all or the major proportion of the resin, aromatic polyimide, its
modified resin, such as polyamide-imide, polyether-imide, and
polyester-imide, and phenol resing are s used. The proportion of the resin
is preferably from 20 to 70% by weight based on the additives.
A solid lubricant other than the above mentioned, can also be included in
the additives. Other solid lubricants can be tungsten disulfide
(WS.sub.2), BN, PTFE, iluorine plastics, or Pb. Their additive amount is
from 3 to less than 20% by weight, preferably from 5 to 20% by weight.
When a solid lubricant is used, the lowest content of molybdenum disulfide
must be set at 20% by weight.
A method for producing the above described sliding material is hereinafter
described.
A powder of lead bronze or the like, having particle diameter -100 mesh and
+200 mesh, is dispersed on a steel backing to provide a thickness of
approximately 300 .mu.m. The bronze particles are piled into three
particle-layers in this example. The sintering is carried out at
800.degree. to 850.degree. C. As a result, a sintered layer having a
porosity of from approximately 40 to 50% is obtained. The steel backing,
on which the sintered layer is bonded, is immersed in the liquid
containing the solid lubricant and resin. It is necessary to thoroughly
replace the air contained in the pores of the sintered layer with resin,
because the remaining or non-replaced air may cause cracking when the
workpiece is later subjected to drying. The liquid is stirred with a mixer
to impregnate the pores of the sintered layer with the solids. According
to another impregnating method, the solid lubricant and resin are mixed in
liquid, and the liquid mixture is applied on the sintered layer.
Drying is then carried out at 150.degree. C. for 30 minutes. The solvent of
the resin vaporizes during drying. When the solvent is used in a great
amount, the replacement of air in the sintered layer pores becomes easy.
But, since the viscosity of the resin is lowered, vaporization of the
solvent is so impeded as to elongate the drying time. In this regard,
since the phenol resin has a low viscosity, for example, 2p, even if its
solid content is as high as 60%, the air can be thoroughly replaced and
the drying time can be shortened by using the s phenol resin. The drying
time in the case of phenol resin can be shortened to 1/6 times as low as
in the case of using polyamide-imide. As a result, the line speed of the
drying plant can be enhanced and products free of swell and cracks can be
produced.
After drying, baking is carried out at, for example, 300.degree. C. for 30
minutes. Subsequently, the surface of the workpiece is removed by
machining at a depth of approximately 100 .mu.m from the surface. The
sintered metal-layer is exposed by approximately 70% on the surface of the
sliding layer.
In in order to obtain a sintered layer having 50% or more of porosity, the
mixed powder of lead bronze and graphite are dispersed on the metal
backing, and are sintered at 800.degree.-850.degree. C. in a hydrogen
stream, and, then, the non-sintered remaining graphite powder is sucked up
by a dust collector. In addition, the porosity of 50% or more of the
sintered layer can be attained also by using subliming material, e.g.,
melamine cyanurate which sublimes at a temperature of from 300.degree. to
500.degree. C.
Non-sintered graphite can be used as the solid lubricant. In this case,
none of it is sucked up by the dust collector.
Although lead bronze is described as an example of the sintered metal,
other metals can be sintered in the same manner.
The sliding properties of the material according to the present invention
are described from a theoretical aspect.
The additives adhere to the sintered layer of the sliding material which
has been subjected to the seizure test described in the examples. When the
solid lubricant is more than 30%, the amount of adhesion is greater than
in the case where the solid lubricant is less than 30%. These facts can be
construed as follows.
Heat generation at the sliding surface due to friction increases under
severe sliding conditions. Resin, which has a higher coefficient of
thermal expansion than bronze, seems to protrude from the sliding surface
higher than the sintered layer. The protruding resin then flows onto the
sintered layer and adheres to said layer. When the solid lubricant is less
than 30%, the bonding strength due to the resin is high. In this case, the
flowing and adhesion of the resin as described above occur with
difficulty. On the other hand, when the solid lubricant is more than 70%,
since the bonding strength due to the resin is weak, the wear of the
additives occurs at a greater rete as compared with the flow and adhesion
of the resin. This means that wear resistance is impaired.
The resin filled in the pores therefore not only bonds the solid lubricant
but also causes adhesion of the additives on the exposed sintered layer,
which adhesion is effective in enhancing the wear resistance and seizure
resistance.
Generally speaking, the molybdenum disulfide (MoS.sub.2) has a smaller
particle diameter than the graphite. The molybdenum disulfide is a
hexagonal crystal which is liable to cleave. The particles of molybdenum
disulfide adhered to the sintered layer, is divided finely by the shear
stress generated due to friction between the shaft and bearing. The
so-finely divided is particles lubricate between the shaft and bearing.
Because of these properties of the molybdenum disulfide, it cannot improve
the wear resistance as effectively as graphite does. Meanwhile, graphite
is similar to molybdenum disulfide in that it has hexagonal crystals whose
cleavage is easy. The former is, however, harder and greater in particles
than the latter. The bonding strength between resin and graphite is high.
Because of these properties, wear resistance can be effectively enhanced
by the graphite. Both wear resistance and seizure resistance are
synergistically improved by using both graphite and molybdenum disulfide.
The present invention is described hereinafter with reference to the
examples and comparative examples.
EXAMPLE 1
Spheroidal lead-bronze powder having a composition of 80% of Cu, 10% of Sn
and 10% of Pb, polyamide-imide (a product of Hitachi Kasei, Hl-500 or
HpC-6000-26), graphite (product of Tokai Carbon, G152 or TGP-15), and
MoS.sub.2 (a product of Sumiko Lubricating Inc., PA powder) were used to
produce by the above described method various sliding materials, whose
machining depth was 100 .mu.m and whose exposed area of the sintered layer
was 75% by area. Flat-sheet samples were prepared from the slidng
materials and were brought into the line contact with the opposed
material, which was a cylindrical rotating shaft (quenched S45C).
The testing conditions were as follows.
(1) Wear-resistant Test
Load: 10 kg
Speed: 2 m/sec
Lubrication: 5 cc/min (oil supply)
Kind of oil: paraffin oil
Sliding distance: 1.44.times.10.sup.4 m
(2) Seizure-resistance Test
Load: 10 kg
Speed: 4 m/sec
Lubrication: after supplying oil at a rate of 0.1 cc/min the oil supply was
cut.
Kind of oil: paraffin oil
For the purpose of reference, the testing conditions in Japanese Examined
Patent Publication No. 63-37445 referred hereinabove are given.
Load: 250 g
Speed: 0.052 m/sec
Lubrication: grease
it is apparent from the comparison of this condition with the conditions
(1) and (2) that the testing conditions according to the present invention
are under a high load, high speed and severe lubrication conditions. These
testing conditions are boundary lubricating condition. As a result of the
tests, the following wear-amount (volume wear in mm.sup.3) and seizure
time (time after the oil cut to seizure) were obtained.
TABLE 1
______________________________________
Wear Seizure
Materials Amount (mm.sup.3)
Time (min)
______________________________________
Inventive A
MoS.sub.2 (wt %) 25 0.08 55
Graphite (wt %) 25
Polyamide (wt %) 50
imide
Inventive B
MoS.sub.2 (wt %) 40 0.1 60
Graphite (wt %) 10
Polyamide (wt %) 50
imide
Comparative A
MoS.sub.2 (wt %) 50 0.9 50
Polyamide (wt %) 50
imide
Comparative B
Graphite (wt %) 50 0.08 20
Polyamide (wt %) 50
imide
Comparative C
MoS.sub.2 (wt %) 10 0.3 16
Graphite (wt %) 10
Polyamide (wt %) 80
imide
______________________________________
Another test was carried out under the following conditions.
(b 3) Seizure resistance test
Load: 10 kg
Speed: 4 m/sec
Lubrication: After mist-lubrication for 5 minutes, the supply of mist was
cut
Testing time: 2 hours
TABLE 2
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Materials Seizure time (min)
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Inventive C
MoS.sub.2 20 wt % more than 120
Graphite 20 wt %
Phenol 60 wt %
Inventive D
MoS.sub.2 20 wt % more than 120
Graphite 20 wt %
Polyamide 60 wt %
imide
Comparative D
Lead bronze 10
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As is apparent from the above test results, the wear resistance of the
inventive examples, in which both molybdenum disulfide and graphite are
used in an amount of 50% or more, is excellent.
EXAMPLE 2
The Inventive Material A, mentioned above, was prepared to exhibit various
values on the exposed area of the sintered layer. The seizure resistance,
wear resistance and coefficient o of friction of the so-prepared samples
were measured under the above described testing conditions except for the
lubrication. The lubrication was set so that mixed oil containing 1 volume
of ice machine oil and 9 volumes of light oil was fed as mist for 5
minutes, and then the oil supply was cut. The test results are shown in
FIGS. 1 through 3.
As is apparent from FIG. 1, seizure-resistance decreases drastically when
the exposed area of the sintered layer exceeds 95%. The seizure resistance
is stable when the exposed area of the sintered layer is 80% or less.
As is apparent from FIG. 2, the wear amount increases when the exposed area
of the sintered layer is less than 10%. This is because the resin and
solid lubricant are liable to separate from the sliding surface when the
exposed area of the sintered layer is small. On the other hand, when the
exposed area of the sintered layer is more than 90%, the wear amount
increases. This is because seizure tends to occur.
As is apparent from FIG. 3, the coefficient of friction increases when the
exposed area of the sintered layer is less than 10%. This is because the
resin is liable to separate from the sliding surface when the exposed area
of the sintered layer is small. This separation occurs in such a manner
that lumps of resin are scraped from the sliding surface. On the other
hand, when the exposed area of the sintered layer is more than 90%, the
coefficient of friction decreases. This is because, along with the
increase in the wear amount, the sliding surface increases to reduce the
surface pressure. Under this condition, the lubricating condition shifts
toward fluid lubrication, under which the coefficient of friction is low.
EXAMPLE 3
The sliding materials having the compositions given in Table 1 were
produced by the method described above. Wear resistance and seizure
resistance were tested by the methods described above.
The physical properties of the sliding layer were as follows.
(1) Thickness of sliding layer: 200 .mu.m
(2) Porosity: 35% (volume)
(3) Exposed area of sintered layer: 70% (area)
(4) particle diameter of sintered metals: 110 .mu.m (average)
The test results are given in Table 3.
TABLE 3
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Composition Wear Seizure
Resin MoS.sub.2
Graphite
Others Resistance
Resistance
No. (%) (%) (%) (%) (mm.sup.3)
(min)
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1 PAI = 20
50 30 -- 0.12 74
2 PAI = 20
40 20 -- 0.09 66
PESI = 20
3 PAI = 50
10 40 -- 0.08 57
4 PAI = 50
25 25 -- 0.08 60
5 PAI = 50
40 10 -- 0.10 62
6 PAI = 50
48 2 -- 0.25 67
7 PAI = 60
20 20 -- 0.12 50
8 PI = 60
35 5 -- 0.19 60
9 PEI = 70
15 15 -- 0.15 60
10 PAI = 70
20 10 -- 0.17 52
11 PI = 20
50 11 Pb = 19
0.11 77
12 PAI = 30
27 40 BN = 3 0.09 59
13 PAI = 50
20 20 PTFE = 10
0.09 66
14 PAI = 50
40 2 WS.sub.2 = 2
0.23 65
BN = 2
PTFE = 2
Pb = 2
15 PESI = 50
30 10 WS.sub.2 = 10
0.09 59
16 PI = 5
10 35 BN = 5 0.08 59
PAI = 45
17 PAI = 50
15 20 WS.sub.2 = 5
0.08 62
PTFE = 10
18 PAI = 20
20 15 PTFE = 5
0.12 74
19 PEI = 60
10 15 BN = 2 0.12 56
PTFE = 3
20 PAI = 70
15 10 PTFE = 5
0.15 54
21 PAI = 50
50 -- -- 0.15 60
22 PAI = 50
-- 50 -- 0.09 20
23 PAI = 80
10 10 -- 0.38 16
24 Ph = 60
20 20 -- 0.12 50
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